1. Field of the Invention
This invention relates to freewheel hubs, especially on bicycles.
2. Description of Prior Art
Bicycles normally have a freewheel hub on the rear wheel. Foot pedals on cranks drive one or more forward sprockets or chain rings, which drive a chain loop, which drives one or more rear sprockets mounted on a sprocket hub on the rear axle that drives the wheel hub. When a rider stops pedaling, the hub xe2x80x9cfreewheelsxe2x80x9d or turns freely in the forward direction independently of the sprockets, so the pedals do not keep turning with the wheels. This allows a rider to relax or concentrate on steering without constant leg motion. In general, a freewheel hub can be provided on any powered wheel of a velocipede, or pedal-powered vehicle.
A bicycle axle is mounted between two bicycle frame members. A conventional freewheel hub includes a hub shell rotationally mounted on the axle, and a sprocket hub mounted beside the hub shell to co-rotate with the hub shell in the drive direction, and to rotate independently of the hub shell in the coasting direction. The hub shell supports a wheel via spokes or a plate. The sprocket hub supports one or more sprockets for the drive chain.
The sprocket hub drives the hub shell via a circular ratchet ring and pawls. For this purpose, a drive assembly is attached to the hub shell, and extends into the sprocket hub. The drive assembly receives rotational force from the sprocket hub, and transfers it to the hub shell. Thus the drive assembly must be firmly indexed to the hub shell. Pawls are mounted on the drive assembly, and a ratchet ring is mounted on the interior of the sprocket hub, or vice versa. The sprocket hub can wobble on the drive assembly due to normal play in the sprocket hub bearings, and the fact that these bearings are close together. This causes friction and wear on the drive assembly. The drive assembly exerts torsion on one end of the hub shell. This twists the hub shell, and works the connection between the drive assembly and hub shell with each pedal cycle, causing the connection to loosen. Thus, rigidity of the assembly is lost, resulting in friction, wear, wobble, metal fatigue, and failure. Examples of the prior art are shown in U.S. Pat. Nos. 5,458,223 and 5,518,096. Both of these patents attempt to solve the above problems of instability and loosening between the hub shell and the drive assembly. However this is done with an increment of the prior technology by mounting the driving assembly more firmly to the hub shell, rather than by the new technology herein.
Other prior patents show various designs of freewheel hubs. Some of these are complex, and none of them provide the advantages of the present invention as summarized below.
The main objective of the invention is a freewheel hub design for bicycles with a more stable sprocket hub and less twist and loosening of the hub assembly than occurs in prior designs. Further objectives include simplicity, practicality, and lightness of weight.
These objectives are achieved in a freewheel hub for bicycles with an inner drive cylinder 5 that supports a hub shell 1. A sprocket hub 10 is mounted on one end of the cylinder, and may be integral with it. A bearing 2 at each end of the axle supports the cylinder and sprocket hub for rotation about the axle 1. Outer bearings 16 between the cylinder and hub shell rotationally support the hub shell. A circular ratchet 8 in the interior of the hub shell, and corresponding pawls 6 on the exterior of the cylinder, drive the hub shell when torque is applied to the sprocket hub, and allow the shell to freewheel otherwise. A more central position of the pawl drive in the hub shell than in prior designs reduces twist of the shell. Wide separation of the bearings supporting the sprocket hub and cylinder provide a stable sprocket hub. These features provide maximum transmission efficiency and reliability.